It is evident from a glance at any pocket calculator that the minimum size of such apparatus is determined by the keyboard and by the display arrangements; not by the electronics within the device. Of the two determining factors, the keyboard occupies, by far, the greater amount of surface space. With maximum surface dimensions of about three and one-half inches by seven inches, space available for a full spectrum of function keys is at a premium. Particularly when the human factors are considered and minimum key size is determined, it is clear that fewer keys are employed than would otherwise be permitted by the electronics within the calculator. Space within the calculator goes unused instead.